81981998208 has 256 divisors, whose sum is σ = 264736512000. Its totient is φ = 24769704960.

The previous prime is 81981998191. The next prime is 81981998251. The reversal of 81981998208 is 80289918918.

It is a super-2 number, since 2×81981998208² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 13644741 + ... + 13650747.

It is an arithmetic number, because the mean of its divisors is an integer number (1034127000).

Almost surely, 2^81981998208 is an apocalyptic number.

81981998208 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81981998208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132368256000).

81981998208 is an abundant number, since it is smaller than the sum of its proper divisors (182754513792).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81981998208 is a wasteful number, since it uses less digits than its factorization.

81981998208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6400 (or 6382 counting only the distinct ones).

The product of its (nonzero) digits is 5971968, while the sum is 63.

The spelling of 81981998208 in words is "eighty-one billion, nine hundred eighty-one million, nine hundred ninety-eight thousand, two hundred eight".